It went through a hype cycle, and then people sort of moved on - into IoT. And IoT, naturally, just sounds better and is more accessible, plus the tech did catch up, so it became a lot more popular than WSN (the term).
I told a friend of mine that no one paid attention when the field was called WSN, and now it is the exact same thing, but IoT is taking off like crazy. (At that point, I had left research altogether). He said "Yes, and that's perfectly reasonable. If you don't invent new terminology every few years and manufacture some kind of new hype, the funding agencies stop sending you money."
This is a community which is based on the mantra of "making something users want". Once you realize that the upstream user here is the funding agency, and what they really want is to make bets on "cool stuff for tomorrow" rather than boring old 3-5 year old tech (such as WSN), the hype actually makes perfect sense.
Sure, there is still a need to separate the snake oil from the reality. But that is true of tech in general. I am not sure if AI/ML is particularly bad in some way.